1. Field of the Invention
This invention relates to the art of dot display assemblies, and more particularly concerns a changeable dot display assembly capable of assuming three different dot display positions, and useful as part of a large matrix of revolving disks which can serve as a variable message sign for a shopping mall, highway, theater, restaurant, or other public viewing installation.
2. Description of the Prior Art
Dot display assemblies now available are generally designed to present either one of two different display faces. These display assemblies utilize as a basic display element, a rotatable disk which is rotated 180 degrees by electromagnetic means actuated by appropriate electrical or electronic circuitry. The display disk usually has one black side and an opposite fluorescent colored side and carries a permanent magnet. When the display disks in a matrix are selectively turned to either one of their two viewing positions different messages may be exhibited. Such a prior dot assembly may have a stationary U-shaped magnetic core on the two legs of which each may have one coil. The coils are each one half of a single continuous coil. When electric current passes through the coil in one direction, the cores present magnetic poles of opposite polarity to an adjacent rotatable disk, to turn the disk to one display position. When the coil current is reversed in direction, the magnetic polarities of the legs of the core reverse to turn the display disk to its other, second display position 180 degrees from the previous position. This type of prior dot display assembly is not capable of turning the disk to a third dot display position, as is possible in the present invention.